Technical Abstract:
Sugarcane (Saccharum spp.) breeders are looking for new sources of germplasm with desirable genes to overcome abiotic and biotic stresses and to increase the sugar content and yield potential for developing cultivars for sucrose and bioenergy. One untapped source of desirable genes would be the germplasm collection referred to as the “World Collection of Sugarcane and Related Grasses” (WCSRG) located at the USDA-ARS Subtropical Horticulture Research Station in Miami, FL, which is one of two sugarcane germplasm collections in the world. It is a collection of approximately 1,200 accessions from 45 countries including Saccharum germplasm with 20 different species, the most abundant being S. spontaneum, S. officinarum and S. hybrids. The objectives of this research were to evaluate accessions in the WCSRG phenotypically and then combine this phenotypic data with the genotypic data of colleagues to create a core collection representing most of the diversity of the WCSRG. By intense phenotypic evaluation of each accession in the WCSRG, we would then have a reasonable means of identifying the full phenotypic potential of the full WCSRG. Phenotypic measurements taken of all accessions in the collection were: stalk height, stalk diameter, internode length, stalk color, percent flowering, leaf sheath pubescence, inner stalk aerenchyma and pith, Brix, and presence of Sugarcane yellow leaf virus. Phenotypic observations revealed high Brix in 18 S. spontaneum accessions, with a mean Brix of 14.7% compared with 9.0% for all of the spontaneums in the collection that contained extractable juice. We also found 5 Erianthus and one Miscanthus accessions with high Brix (mean = 14.2%). There were 649 plants (57.3% of the population) that had no serological detectable levels of Sugarcane yellow leaf virus as compared to > 99% of commercial sugarcane cultivars in Florida being susceptible to this disease. For core collection selection, data were analyzed using the M strategy and Shannon coefficients with MStrat software. There were 300 accessions, including at least one accession representing all the known species present in the WCSRG that were selected into the core collection. The Shannon Score for the selected core collection was 31.30 and the Shannon score for the complete WCSRG was 32.17. Thus, according to the Shannon scores, our core collection retains 97.30% (100x31.30 /32.17) of the diversity of the WCSRG. To learn more about the potential of the WCSRG to contribute to improvements in bioenergy and sugarcane breeding and to identify molecular markers associated with important traits, we made minor modifications to the core collection (deleted some distant species and replaced them with S. officinarums) to form a mapping panel. In the next years, extensive measurements will be made on the mapping panel. Based on yield, stress tolerance, and flowering information in the core collection, immediate attention will be given to identifying S. spontaneums with high Brix as useful parents and other parents among all the species for use as sources of resistance to Sugarcane yellow leaf virus.